In U.S. Pat. No. 5,408,704 (the disclosure of which is hereby incorporated by reference herein) a low volume vacuum toilet assembly is provided which can fit in vehicles and boats where vacuum toilets were previously impractical, while also providing minimum water usage. While the assembly shown therein is eminently practical and desirable, there are a few aspects of the vacuum tank construction and relationship with the vacuum pump that are less than optimum for some circumstances.
According to the present invention a vacuum tank, particularly for use in association with a vacuum toilet assembly, is provided which retains the low volume characteristics of the structures disclosed in U.S. Pat. No. 5,408,704 while having other advantages associated therewith that make the vacuum tank, and vacuum tank and pump assembly, more versatile and effective.
According to the present invention, the vacuum tank is constructed, and positioned with respect to the vacuum pump, so that there is an optimized washing effect of water and waste into the vacuum tank. The inlet is located at the opposite end of the tank from a sump area that is formed in the tank bottom, so that the entering waste washes down to the sump carrying all materials with it. This washing effect keeps the tank from building up deposits of tissue which would reduce the vacuum capacity and performance efficiency. Also, a substantially rigid dip tube is provided in the tank having a generally oval-shaped bottom portion thereof mounted just above the sump and positioned in such a way that objects of a size that would damage the pump cannot pass into the dip tube, while still effectively allowing the free passage of liquid and waste into it.
The vacuum pump is mounted on a top surface of the vacuum tank, and is--as in said U.S. Pat. No. 5,408,704--directly connected to the vacuum tank outlet. The tank includes a generally vertically extending portion which has an inner sidewall in which the outlet opening is formed, and from which the dip tube extends. The dip tube and pump are mounted so that they may be readily detached from each other using a spin nut, and the dip tube itself can be readily removed since it has a plug connection to the outlet opening which is sealed by a pair of O-rings.
The vacuum tank inlet has a fitting associated with it which also is readily replaceable, having a double O-ring construction, and in the form of an elbow. The elbow fitting may be rotated at least about 180.degree. with respect to the tank so as to provide great versatility in positioning of the elements and connection up to the vacuum toilet, and a recessed area is provided in the tank vertically extending portion to allow the inlet hose to extend through it so as to provide ready attachment to the rotatable elbow fitting.
The tank is of plastic and has a nominal wall thickness of 5/16th inch. All flat surface areas are limited to under about 80 square inches in area so that there will not be significant deflection, and to provide the lightest tank possible with high structural integrity. The tank may be made of polyethylene or polypropylene, or any other suitable plastic, with such a construction not being limited to any particular plastic.
According to one aspect of the present invention a vacuum toilet assembly is provided comprising the following elements: A vacuum toilet having a waste discharge normally closed by a vacuum-tight valve. An actuator for the vacuum-tight valve. A vacuum tank having a first top surface, a bottom, a length, a width, an inlet, and an outlet. A waste tank having an inlet and an outlet. A vacuum pump having an inlet and an outlet. A first hose connecting the waste discharge of the toilet, adjacent the vacuum-tight valve, to the vacuum tank inlet. A second hose connecting the vacuum pump outlet to the waste tank inlet. The vacuum tank outlet directly connected to the vacuum pump inlet. And, the vacuum pump mounted on the first top surface of the vacuum tank.
The vacuum tank inlet is on the opposite side of the vacuum tank outlet along the length of the tank, and also along the width of the tank. The pump is mounted on the vacuum tank between the vacuum tank inlet and outlet along the length of the tank. The vacuum tank preferably further includes a vertically extending end portion, extending upwardly from the first top surface, having a second top surface and an inner sidewall facing the vacuum tank inlet, the vacuum tank outlet disposed in the inner sidewall. The vacuum tank inlet is in the first top surface, and a substantially 90.degree. elbow fitting is sealingly rotatably mounted in the vacuum tank inlet (having an arc of rotation of at least about 180.degree.), and connected to the first hose.
A dip tube assembly, including a substantially rigid dip tube which extends from the vacuum tank outlet to just above the vacuum tank bottom, is also provided. The dip tube comprises a substantially circular cross-section plastic pipe which has a portion thereof elongated along an axis of elongation, and having an open end termination remote from the vacuum tank outlet. The end termination is cut at an angle to the axis of rotation so as to define a substantially oval-shaped opening which is above, but spaced from, the vacuum tank bottom, and makes an angle of about 20.degree.-40.degree. (preferably about 30.degree.) with respect thereto. The dip tube typically has a substantially J-shaped configuration and a spin nut connection is provided between the dip tube assembly and the vacuum pump inlet.
The vacuum tank bottom preferably comprises a sump located in substantially the middle of the vacuum tank width, and approximately below the inner sidewall, the end termination opening of the dip tube disposed above the sump and positioned with respect to the sump so that objects of a size that would harm the vacuum pump cannot pass between the vacuum tank bottom and the open end termination into the oval-shaped opening, yet liquid and waste may readily pass therethrough. The dip tube may have an open cross-sectional area of about 3.5-4 square inches (e.g. about 3.8 square inches), with a maximum spacing of the dip tube, at the oval opening, from the sump of about 3/4 of an inch. The dip tube assembly also comprises a double O-ring plug, the plug sealingly and readily removably connecting the dip tube assembly to the vacuum tank outlet. The tank typically has four feet extending downwardly from the bottom of the tank and supporting the sump off of a flat substantially horizontal support surface (e.g. in a boat or recreational vehicle). The elbow fitting also comprises a mounting portion having a double O-ring seal which extends substantially vertically and about which the oval fitting is sealingly rotated.
The invention also relates to a vacuum tank comprising: A first top surface, a bottom, a width, a length, an inlet, an outlet, a vertically extending end portion, extending upwardly from the first top surface and having a second top surface and an inner side wall facing the vacuum tank inlet. The vacuum tank outlet in the inner side wall. The vacuum tank inlet in the first top surface. Wherein the vacuum tank inlet is on the opposite side of the vacuum tank from the vacuum tank outlet along the length of the vacuum tank. Wherein the vacuum tank inlet is on the opposite side of the vacuum tank from the vacuum tank outlet along the width of the vacuum tank. And, wherein the vacuum tank bottom comprises a sump located in substantially the middle of the vacuum tank width, and approximately below the inner side wall, remote from the vacuum tank inlet.
Preferably the vacuum tank is of plastic having a nominal wall thickness of about 5/16th inch and flat surface areas, the maximum area of any flat surface area being about 80 square inches, so that there is no significant deflection of the tank walls during generation of the vacuum in the tank. The tank is also typically associated with a vacuum switch which automatically shuts off the vacuum pump at a vacuum of about ten inches of mercury, and turns the pump back on if the vacuum falls to below about eight inches of mercury. The vacuum tank has the preferred dip tube assembly described above mounted in association therewith, and the vacuum pump mounted thereon as also described above.
It is the primary object of the present invention to provide a vacuum toilet assembly, and a vacuum tank for use with a vacuum toilet assembly, that has optimum flexibility in mounting and location, low volume configuration, and optimized washing effect of water and waste therethrough. This and other objects of the invention will become clear from an inspection of the detailed description of the invention and from the appended claims.